Cliffs and coasts Flashcards

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1
Q

Overtime what causes cliffs to retreat?

A

weathering and erosion

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2
Q

What direction is the swash in longshore drift

A

It is in a diagonal line towards the prevailing wind

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3
Q

What direction is the backwash?

A

at a right angle to the beach, perpendicular to the swash and it is pulled back due to gravity

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4
Q

what is a constructive wave?

A

a wave with a strong swash, a weak backwash, it created a wide gently sloping beach, low in height and are less steep

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5
Q

what is a destructive wave?

A

has a weak swash and a strong backwash, breaks more frequently compared to constructive waves, more material is being removed than placed, tall and toppling, create a steep and narrow beach

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6
Q

what does the wave energy depend on?

A

the fetch

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7
Q

what is in situ?

A

in place

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8
Q

what is an example of something that is in situ?

A

weathering

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9
Q

What are the types of weathering?

A

biological
freeze - thaw
chemical

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10
Q

what are bedding planes?

A

they are horizontal joints with weaknesses which can be exposed by waves or weathering which could cause rock falls

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11
Q

what are vertical joints?

A

vertical which can cause whole sections of the cliff to fall of

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12
Q

why are some bedding planes less likely to collapse?

A

because they are tilted away

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13
Q

what are the ways cliffs fall?

A

slumping
falling
sliding

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14
Q

What happens when a cliff slides?

A

a whole column of material moves in one and will go without warning, it usually happens in vertical joints

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15
Q

what happens when rock falls on a cliff?

A

when freeze - thaw weathering makes the gaps in the rocks unstable and they get taken down by gravity it can only happen on a hard rock cliff

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16
Q

what happens when cliffs slump?

A

when a permeable rock is bellow an impermeable rock, if it becomes water logged it will slump in a curved movement it only happens in soft rock cliffs

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17
Q

what does hydraulic action cause?

A

cavitation

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18
Q

what coastline do headlands and bays form?

A

discordant coastline

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19
Q

How are headlands and bays formed?

A

when there are strips of hard and soft rock on a discordant coastline, the soft rock erodes faster creating a bay and headlands form when the hard rock is barely eroded.

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20
Q

what is a discordant coastline?

A

this is where the coastline is made up of bands of hard rock and soft rock, they are usually at right angles to the coastline

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21
Q

what is a concordant coastline?

A

where the coastline is made up of a continious line of rock parallel to the coastline

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22
Q

what happens when waves approach a disconcordant coastline?

A

the energy is concentrated on the harder rock, headlands, so there is more erosion creating caves, cracks, stacks, arches and stumps

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23
Q

How does a cave form

A

when a weakness is exposed in the headland and gets eroded by the waves

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24
Q

what is an example of an arch?

A

durdle door

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25
Q

how is an arch formed?

A

when rock is eroded by hydraulic action, abrasion and freeze - thaw weathering

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26
Q

how is a stack formed?

A

when the rock can no longer support its weight due to freeze - thaw weathering, it collapses

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27
Q

when is a stump formed?

A

when a stack is eroded and weathered over time

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28
Q

what is an example of a stack

A

old harry rocks

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29
Q

where are wave cut platforms found?

A

at the base of the headland

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30
Q

how is a wave cut platform formed?

A

rocks are hurled at the base of a cliff creating a wave cut notch
the top of the cliff will become unstable which means that the overhang will collapse into the sea providing more material for abrasion and attrition
the cliff retreats which leaves behind a rock platform - a wave cut platform - that is exposed in low tides

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31
Q

how is a rock pool formed?

A

when a boulder lodges in a depression in the rock of a wave cut platform and grinds a hollow as it rolls around in the waves after some time the depression becomes dep enough to hold water during low tide

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32
Q

what type of erosion forms a rock pool?

A

abrasion

33
Q

when does deposition occur on the coast?

A

when waves are constructive - the swash is greater than the backwash

34
Q

what process travels sediment along the beach?

A

longshore drift

35
Q

what results in a beach?

A

lots of deposition

36
Q

what is longshore drift?

A

when the prevailing wind causes a swash and then gravity causes a backwash in a right angle to the coast. This happens in a zig zag movement and it picks up the sediment and moves it from the side of the beach

37
Q

what two processes form a floodplain?

A

lateral erosion and deposition

38
Q

how is a spit formed?

A

when longshore drift transports material along beach and the coastline changes in direction.
As the material enters shallow water there is a slight drop in energy that will deposit material at a faster rate that it can be removed, gradually a ridge is built up.
A change in prevailing wind direction causes the spit to become hooked.
Water is trapped behind the spit creating a low energy zone as the water begins to stagnate mud and marshland develop behind the spit.
The marshland behind the spit is colonised by grasses and plants that are salt water tolerant.
Spits continue to grow until deposition can no longer occur.

39
Q

what are wooden revetments?

A

wooden slatted barriers constructed towards the rear of cliffs, energy from waves is dissipated by them breaking against the revetments.

40
Q

what are the advantages of wooden revetments?

A

less beach material is eroded compared to a sea wall
cheaper and less intrusive than a sea wall

41
Q

what are the disadvantages of a wooden revetment?

A

short life span
unsuitable where wave energy is high

42
Q

what is an offshore breakwater?

A

it is located of shore to change the direction of waves and reduce longshore drift, they also help absorb wave energy.

43
Q

what are the advantages of offshore breakwater?

A

beaches retain natural appearance

44
Q

what are the disadvantages of offshore breakwater?

A

difficult to maintain
unattractive
does not protect the cliffs directly
does not stop beach material from being eroded

45
Q

what is cliff stabilization?

A

cliff drainage takes excess water from the cliff so that the cliff does not become saturated and heavy, anchoring involves planting vegetation, terracing or wiring to hold cliffs in place

46
Q

what are the advantages of cliff stabilization?

A

relatively cheap
very effective
aesthetically pleasing
does not spoil the natural look of the beach

47
Q

what are the disadvantages of cliff stabilization?

A

does not stop waves reaching the cliff face - the problem will still occur

48
Q

what is beach nourishment?

A

beaches are made higher and wider by importing sand and shingle to an affected area that was affected by longshore drift

49
Q

what are the advantages of beach nourishment?

A

cheap
retains the natural appearance of the beach
pressurves the natural appearance of the beach

50
Q

what are the disadvantages of beach nourishment?

A

shingle increases erosion in other areas
large storms will require beach replenishment increasing cost

51
Q

what is sand dune stabilization?

A

when sand dunes are fenced of and new species are planted so that they provide a natural defence of flooding

52
Q

what are the advantages of sand dune stabilization?

A

aesthetically pleasing
retains natural appearance of the beach
cheap

53
Q

what are the disadvantages of sand dune stabilization?

A

specific plants are needed to live in dune habitats
the success of dune stabilization is not always guaranteed

54
Q

what is managed retreat?

A

areas of coast are allowed to erode and flood naturally, usually the places will be considered low value

55
Q

what are the advantages of managed retreat?

A

can be cheaper in the long term as does not need to be maintained
retains natural balance of the ecosystem
eroded material encourages the development of beaches

56
Q

what are the disadvantages of managed retreat?

A

people will lose there livelyhood
people will need compensation
some farmers are unwilling to sell
cannot be used in well developed areas

57
Q

where is the Jurassic coastline located?

A

in the south west of England, it streches from Exmouth to Swanage and is in Devon and Dorset, next to the English channel

58
Q

what is consolidated rock?

A

old rock is more compacted

59
Q

what is unconsolidated rock?

A

rock that is younger and is less compacted

60
Q

what is the geology of the Jurassic coast?

A

hard rock which is consolidated

61
Q

what is the climate like in the Jurassic coast?

A

exposed to prevailing winds from the atlantic ocean
prolonged rainfall makes clay heavier and more prone to slumping
annual rainfall is low
warm summers and mild winters

62
Q

what is the human activity like in the Jurassic coast?

A

it has groynes, sea walls, quarrying, gravel extraction, Dorset coast is a major tourist attraction

63
Q

how much erosion takes place per year in the Holderness coastline?

A

2 meters

64
Q

where is the Holderness located?

A

north east of England, east Yorkshire, between Flamborough head and Spurn head, next to north sea

65
Q

what is the geology of the Holderness coast?

A

very soft rock
very young rock - consolidated rock
only hard rock on Flamborough head

66
Q

What human activity has happened in the Holderness coast?

A

sea walls, rock islets, groynes

67
Q

what is the definition of cliff retreat?

A

the gradual backwards movement of a cliff caused by erosion

68
Q

what is fetch?

A

the distance over which the wind has blown

69
Q

what is biological weathering?

A

when plants and animals burrow/grow in the ground/cliff face that breaks up the coast, it happens in situ

70
Q

what is freeze - thaw weathering?

A

happens when water gets into the crack and freezes, the rock then expands and breaks

71
Q

what is chemical weathering?

A

when rocks react with acid rain and over time it breaks down the rock

72
Q

what is cliff sliding?

A

when a whole colum of material moves in one go

73
Q

what is rock fall?

A

when rock fragments fall from the face of the cliff because of the action of gravity - only happens on hard rock cliffs

74
Q

what is cliff slumping?

A

when a permeable rock is bellow an impermeable rock, if it becomes water logged it will slump away in a curved movement

75
Q

what is lithology?

A

young sedimentary rocks have not been compacted as much as older rocks so they are unconsolidated

76
Q

what is porus?

A

can let water in

77
Q

what is unintended?

A

a side effect of human activity that can affect coastal processes

78
Q

how does an interlocking spur form

A

vertical erosion occurs and creates a v-shaped valley
weathering breaks down the rock on the valley side
weathered material is carried by the river

79
Q

how is a beach formed

A

a constructive wave breaks on the shore of a bay because it has run out of energy
the swash is greater than the backwash so deposition occurs creating as beach